This invention relates to a process for producing metallic chromium by the carbon reduction of chromium oxide wherein plasma is used.
Metallic chromium is generally produced by Thermit reduction of chromium oxide or chromite, or by electrolysis of a chromium salt solution.
It also has been proposed to produce metallic chromium by carbon reduction of chromium oxide wherein chromium oxide briquettes or the like, compression molded from finely divided chromium oxide by using a binder, are heated to a temperature of at least 1,200.degree. C., under vacuum or in a protective atmosphere, in a furnace. This carbon reduction process is, however, not advantageous from the standpoint. That the reduction reaction requires a long period of time and is not efficient. Furthermore, the produced metallic chromium is in a sponge-like form of a small bulk density and, hence, not convenient for being molten in the course of producing Nichrome, heat- and corrosion-resisting steels and other chromium alloys. In addition, when the carbon reduction is conducted under vacuum, evaporation loss of chromium conspicuously occurs because of chromium's enhanced vapor pressure.
A main object of the present invention is to obviate the above-mentioned defects of the known carbon reduction process, i.e. to provide a carbon reduction process wherein the reduction of chromium oxide is efficiently effected in an extremely short period of time.
Other objects and advantages of the present invention will be apparent from the following description.